Temperature Shock | Shock Termico

MIL STD 810 G – Test Method 503.5 – Temperature Shock

 

SCOPE

 

Purpose
Use the temperature shock test to determine if materiel can withstand sudden changes in the temperature of the surrounding atmosphere without experiencing physical damage or deterioration in performance. For the purpose of this document, “sudden changes” is defined as “an air temperature change greater than 10°C (18°F) within one minute.”
Application
Normal environment.
Use this method when the requirements documents specify the materiel is likely to be deployed where it may experience sudden changes of air temperature. This method is intended to evaluate the effects of sudden temperature changes of the outer surfaces of materiel, items mounted on the outer surfaces, or internal items situated near the external surfaces. This method is, essentially, surface-level tests. Typically, this addresses:
  1. The transfer of materiel between climate-controlled environment areas and extreme external ambient conditions or vice versa, e.g., between an air conditioned enclosure and desert high temperatures, or from a heated enclosure in the cold regions to outside cold temperatures.
  2. Ascent from a high temperature ground environment to high altitude via a high performance vehicle (hot to cold only).
  3. Air delivery/air drop at high altitude/low temperature from aircraft enclosures when only the external material (packaging or materiel surface) is to be tested.
Safety and screening
Except as noted in paragraph 1.3, use this method to reveal safety problems and potential flaws in materiel normally exposed to less extreme rates of temperature change (as long as the test conditions do not exceed the design limitations of the materiel).
Limitations
This method does not specifically address the following, but it may, in some cases, be applied through tailoring:
  1. Materiel that will not experience sudden extreme temperature changes to internal components because of its mass, configuration, packaging, installed location, etc.
  2. Replacement of the assessment of performance characteristics after lengthy exposure to extreme temperatures, such as with Methods 501.5 and 502.5.
  3. Temperature shock experienced by materiel transferred between air and liquid or two liquids, the thermal shock caused by rapid transient warmup by engine compressor bleed air, or aerodynamic loading.
  4. This method is inappropriate if the actual transfer time in a service environment will not produce a significant thermal shock.
  5. Materiel that has been exposed to heat from a fire and subsequently cooled with water.
  6. Thermal shock testing that may be considered for safety or hazard assessment of munitions, but that should be accomplished in accordance with MIL-STD-2105C (reference 6.1c).

 

TEST PROCESS

 

Procedure I – Shock from constant extreme temperatures. (Figures 503.5-1 to -3)
Procedure I-A. One-way shock(s) from constant extreme temperature. (Figure 503.5-1)
  • Step 1. With the test item in the chamber in its appropriate logistic configuration, adjust the chamber air temperature to the high or low temperature extreme specified in the test plan (T1) at a rate not to exceed 3°C/min (5°F/min). Stabilize the temperature for a period as determined in accordance with paragraph 2.3.5.
  • Step 2. Transfer the test item in no more than one minute to an atmosphere at temperature (T2) that will produce the thermal shock specified in the test plan, and stabilize the temperature for a period as determined in accordance with paragraph 2.3.5.
  • Step 3. If required in the test plan, evaluate the effects of the thermal shock on the test item to the extent practical.
  • Step 4. If other one-way shocks are required, repeat Steps 1-3. Otherwise, return the test item to standard ambient conditions at a rate not to exceed 3°C/min (5°F/min).
  • Step 5. Examine the test item and, if appropriate, perform an operational check. Record the results for comparison with pretest data. If the test item fails to operate as intended, see paragraph 5 for analysis of results.
Procedure I-B. Single cycle shock from constant extreme temperature. (Figure 503.5-2)
  • Step 1. With the test item in the chamber in its appropriate logistic configuration, adjust the chamber air temperature to the high or low temperature extreme specified in the test plan (T1) at a rate not to exceed 3°C/min (5°F/min). Stabilize the temperature for a period as determined in accordance with paragraph 2.3.5.
  • Step 2. Transfer the test item in no more than one minute to an atmosphere at temperature (T2) that will produce the thermal shock specified in the test plan, and stabilize the temperature for a period as determined in accordance with paragraph 2.3.5.
  • Step 3. If required in the test plan, evaluate the effects of the thermal shock on the test item to the extent practical.
  • Step 4. Transfer the test item back to the T1 environment in no more than one minute. Stabilize the temperature for a period as determined in accordance with paragraph 2.3.5, and evaluate the thermal shock effects (if required).
  • Step 5. Return the test item to standard ambient conditions.
  • Step 6. Examine the test item and, if appropriate, perform an operational check. Record the results for comparison with pretest data. If the test item fails to operate as intended, see paragraph 5 for analysis of results.
Procedure I-C. Multi-cycle shocks from constant extreme temperature. (Figure 503.5-3)
  • Step 1. With the test item in the chamber in its appropriate logistic configuration, adjust the chamber air temperature to the high or low temperature extreme specified in the test plan (T1) at a rate not to exceed 3°C/min (5°F/min). Stabilize the temperature for a period as determined in accordance with paragraph 2.3.5.
  • Step 2. Transfer the test item in no more than one minute to an atmosphere at temperature (T2) that will produce the thermal shock specified in the test plan, and stabilize the temperature for a period as determined in accordance with paragraph 2.3.5.
  • Step 3. If required in the test plan, evaluate the effects of the thermal shock on the test item to the extent practical.
  • Step 4. Transfer the test item back to the T1 environment in less than one minute. Stabilize the temperature for a period as determined in accordance with paragraph 2.3.5, and evaluate the thermal shock effects (if required).
  • Step 5. Repeat steps 2-4 at least twice for a minimum of three cycles.
  • Step 6. Return the test item to standard ambient conditions.
  • Step 7. Examine the test item and, if appropriate, perform an operational check. Record the results for comparison with pretest data. If the test item fails to operate as intended, see paragraph 5 for failure analysis and follow the guidance in paragraph 4.3.2 for test item failure.
Procedure I-D. Shocks to or from controlled ambient temperature. (Figure 503.5-4)
NOTE: This procedural variation always starts at standard ambient conditions, but can be tailored to follow any of the three above variations, i.e., a single shock, a single cycle, or multiple cycles.
  • Step 1. With the test item in its appropriate logistic configuration, stabilize the test item at controlled ambient conditions. (Part One, paragraph 5.1).
  • Step 2. Transfer the test item in no more than one minute to an atmosphere at temperature T1 or T2 that will produce the thermal shock specified in the test plan, and stabilize the temperature for a period as determined in accordance with paragraph 2.3.5.
  • Step 3. Transfer the test item to controlled ambient conditions in no more than one minute, and stabilize the temperature for a period as determined in accordance with paragraph 2.3.5.
  • Step 4. If required in the test plan, evaluate the effects of the thermal shock on the test item to the extent practical.
  • Step 5. Either tailor additional shocks by repeating steps 1-4, or proceed to Step 6.
  • Step 6. After all required shocks are completed, examine the test item and, if appropriate, perform an operational check. Record the results for comparison with pretest data. If the test item fails to operate as intended, see paragraph 5 for analysis of results.

 

NOTE: Tailoring is essential. Please, ask to your confidence laboratory for further details about tailoring of test methods.

 

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